Bhaskar, R. ., S. . Singh, P. . Singh, S. K. . Singh, P. S. . Gaur, and S. . Pandey. “Measurement of Procalcitonin in Acute Exacerbation of COPD and Its Correlation to Spirometric Indices”. International Journal of Research and Development in Pharmacy & Life Sciences, vol. 6, no. 6, Nov. 2017, pp. 2833 -9, doi:10.21276/IJRDPL.2278-0238.2017.6(6).2833-2839.